Rear converter lens

A rear converter lens adapted to be attached on the image side of a master lens system to increase its focal length, the rear converter lens comprising a first lens of negative power, a second lens of positive power and a third lens of negative power;

• wherein said rear converter lens has a negative power as a whole;
• and
• when attached on the image side of said master lens system, allows said first lens to be disposed proximately to said master lens system;
• and
• said rear converter lens conforms to the following conditions:
• 03.<f.sub.1 /f.sub.3 <1
• 0.23<d.sub.4 /.SIGMA.d<0.6
• 0.9<.vertline.f.sub.1 /f.sub.2 .vertline.<1.7
• where f.sub.1, f.sub.2 and f.sub.3 are the focal lengths of the first, second and third lenses, respectively, d.sub.4 is the axial air space between the second and third lens, and .SIGMA.d is the axial space from the first to sixth surface of the rear converter lens.

A rear converter lens adapted to be attached on the image side of a master lens system to increase its focal length, the rear converter lens comprising a first lens of negative power, a second lens of positive power and a third lens of negative power;

• wherein said rear converter lens has a negative power as a whole;
• and
• when attached on the image side of said master lens system, allows said first lens to be disposed proximately to said master lens system;
• and
• said rear converter lens conforms to the following conditions:
• 0.3<f.sub.1 /f.sub.3 <1
• 0.23<d.sub.4 /.SIGMA.d<0.6
• 0.3<.vertline.f.sub.2 /f.sub.3 .vertline.<0.7
• where f.sub.1, f.sub.2 and f.sub.3 are the focal lengths of the first, second and third lenses, respectively, d.sub.4 is the axial air space between the second and third lens, and .SIGMA.d is the axial space from the first to sixth surface of the rear converter lens.

A rear converter lens adapted to be attached on the image side of a master lens system to increase its focal length, the rear converter lens consisting of a first lens of negative power, a second lens of positive power and a third lens of negative power

• wherein said rear converter lens has a negative power as a whole;
• and
• when attached on the image side of said master lens system, allows said first lens to be proximately to said master lens system, and said rear converter lens conforms to the following conditions:
• 0.3<f.sub.1 /f.sub.3 <1
• 0.23<d.sub.4 /.SIGMA.d<0.6
• 0.9<.vertline.f.sub.1 /f.sub.2 .vertline.<1.7
• 0.3<.vertline.f.sub.2 /f.sub.3 .vertline.<0.7
• where f.sub.1, f.sub.2 and f.sub.3 are the focal lengths of the first, second and third lenses, respectively, d.sub.4 is the axial air space between the second and third lens, and .SIGMA.d is the axial space from the first to sixth surface of the rear converter lens.

A rear converter lens adapted to be attached on the image side of a master lens system to increase its focal length, the rear converter lens consisting of a first lens of negative power, a second lens of positive power and a third lens of negative power

• wherein said rear converter lens has a negative power as a whole;
• and
• when attached on the image side of said master lens system, allows said first lens to be proximately to said master lens system, and said rear converter lens conforms to the following conditions:
• 0.3<f.sub.1 /f.sub.3 <1
• 0.23<d.sub.4 /.SIGMA.d<0.6
• 0.9<.vertline.f.sub.1 /f.sub.2 .vertline.<1.7
• 0.3<.vertline.f.sub.2 /f.sub.3 .vertline.<0.7
• 0.3<.vertline.r.sub.1 /F'.vertline.<1.5
• 0.2<.vertline.r.sub.6 /F'.vertline.<0.7
• where f.sub.1, f.sub.2 and f.sub.3 are the focal lengths of the first, second and third lenses, respectively, d.sub.4 is the axial air space between the second and third lens, and .SIGMA.d is the axial space from the first to sixth surface of the rear converter lens, r.sub.1, and r.sub.6 are the radii of curvature of the first and sixth lens surfaces, respectively, as viewed in order form the object side of the rear converter lens, and F' is the focal length of the overall rear converter lens system.

A rear converter lens designed to be attached on the image side of a master lens system to increase its focal length, the rear converter lens consisting of, in order from the side of the master lens system, a first lens of negative power, a second lens of positive power and a third lens of negative power;

• wherein said rear converter lens has a negative power as a whole;
• and
• when attached on the image side of said master lens system, allows said first lens to be located proximately to said master lens system, and said rear converter lens conforms to the following conditions:
• 0.3<f.sub.1 /f.sub.3 <1
• 0.23<d.sub.4 /.SIGMA.d<0.6
• where f.sub.1, and f.sub.3 are the focal lengths of the first and third lenses, respectively, d.sub.4 is the axial air space between the second and third lens, and .SIGMA.d is the axial space from the first to sixth surface of the rear converter lens.